Novel Fenton process of Co-catalyst Co₉S₈ quantum dots for highly efficient removal of organic pollutants

Advanced oxidation processes (AOPs) have been widely accepted as an efficient and promising strategy for treating organic pollutants, is mainly dominated by hydroxyl radicals (•OH); however, its further practical application has been hindered by its low decomposition rate of H₂O₂. Hence, for the first time, we propose an eco-friendly and facile synthesis methodology synthesize water-soluble Co₉S₈ quantum dots (QDs) derived from commercial cobalt disulfide (CoS₂), which can serve as excellent co-catalysts to dramatically enhance the decomposition rate of H₂O₂. It is demonstrated that the conversion rate of H₂O₂ into •OH is ca. 80.02% promoted by Co₉S₈ QDs, whereas the conventional Fenton process is ca. 34.9%. The result shows that unsaturated edged S atoms on the surface of Co₉S₈ play a pivotal role in this enhancement, where the number of protons will react with sulfur atoms to form H₂S and expose reductive metallic active sites to accelerate the Fe³⁺/Fe²⁺ conversion. In addition, to tackle the issue for difficult recovery of liquid quantum dots, the magnetic Co₉S₈ QDs/Fe₃O₄ nanoparticles are particularly synthesized, which show excellent performance for degradation of 20 mg/L Rhodamine B (RhB). Moreover, the TOC degradation rate can remain stable at 80% even after five cycles. It is expected that this work will provide a new pathway of thinking in the Fenton process and impulse the usage of liquid quantum dots in practical AOPs application.